Use of Cemfree concrete for temporary slab piles at Newman St, Westminster

Murphy Ground Engineering installed 750mm and 880mm cased rotary piles up to 34.0m to form a triple storey basement secant wall and bearing piles for a new Hotel development in Westminster. As part of the top down construction methodology and due to limited peripheral space, a temporary slab was designed to accommodate construction plant during the bulk dig and spoil removal.

Due to the loadings on the temporary slab the design required 6# 880mm piles to 25.0m depth to provide support to the slab. As these piles are temporary works in design the use of Cemfree concrete was proposed, although with specific structural requirements it was imperative for the Cemfree concrete to achieve 40N strength at 56 days as well as perform to the required piling concrete characteristics as would be expected. A total of 95m3 of “C32/40” Cemfree concrete was supplied over a period of 4 days to construct the temporary works piles using temp cased rotary bored methodology.

The use of Cemfree at Newman St was aligned with MGE involvement in the LOCOWAG project led by DB Group (Holdings) Limited (DBG). The project is government funded via the Innovate UK scheme and runs from November 2020 to November 2022.

The project will:

– Develop, assess and demonstrate AACM concrete formulations meeting user needs for foundations (buildings and infrastructure).
– Demonstrate and assess use of AACMs in piling to de-risk adoption.
– Carry out laboratory tests to assess durability of AACM concrete formulations in sulfate-rich conditions (and other key performance characteristics), and compare with those of PC-based and other AACM-based concretes, as a driver for new industry-wide guidance/standards (such as BS8500, BRE IP 17/05 and BRE SD1).
– Assess business models and barriers to market and address these.
– Convene an industry Stakeholder group via A3CM to support the production of new industry guidance.